anti run on valves

[Z320]

Hi,

some of you might remember the anti run (petrol) valves I use since years on my TR4A with SU HS6 carbs,

inspired from what most (all?) German (and others) did on cab cars, started as I know with the VW Beetle.

I switch off the fuel directy in the way to the main jet, as Mercedes did that on Stromberg CD175 carbs in the mid 1980-ies.

A number of TR club mates know this and it worked on Michael for 1 year, until he asked me to make a pair for hin.

Sadly the valve is very rare and two are needed, a quick look at the mobile I found ONE at Italy for 250 Euro!

 AND below a model I've never seen, 4 to sell, each 30 Euro!

I had a chat with the seller, bought 2 of them and they arrived today.

Great! I'm very optimistic!

RH on the photo you see the difference to a standard ilde switch off valve (left).

 

Not only the fuel for idle must flow through, but all the fuel.

I guess that works because it is from a 1 carb car, while I us it on 2 carbs.

Not only the valve is differnt: it must be fitted IN Strombergs for a TR6, a pretty interesting new project.

Ciao, Marco

 

[Ian Vincent]

What makes some cars susceptible to running on and others not?  My TR3a with HS6 carbs has never “run on”.

Rgds Ian

[Ralph Whitaker]

6 hours ago, Ian Vincent said:

What makes some cars susceptible to running on and others not?  My TR3a with HS6 carbs has never “run on”.

Rgds Ian

+1, and mine has a TR4 engine with H6 carbs.

Ralph

[Peter Cobbold]

It's called "dieseling":  https://en.wikipedia.org/wiki/Dieseling#:~:text=Dieseling or engine run-on,igniting it without a spark.

If an 'over-run' valve is fitted in the butterfly I guess dieseling could be a problem, but these were a late modification to SUs, an anti-pollution measure.

Peter

[Z320]

2 hours ago, Peter Cobbold said:

It's called "dieseling":  https://en.wikipedia.org/wiki/Dieseling#:~:text=Dieseling or engine run-on,igniting it without a spark.

If an 'over-run' valve is fitted in the butterfly I guess dieseling could be a problem, but these were a late modification to SUs, an anti-pollution measure.

Peter

[Peter Cobbold]

1 hour ago, Z320 said:

 

Those over-run valves would not - I think- be fitted to the original TR4 carbs. Their function is to admit a combustible mixture on the over-run, reducing unburned exhaust pollution. Engine braking is reduced.  The discs can be soldered onto the butterly  but solder does not like alcohol in modern fuels, Better to fir a solid butterlfy.  Peter

[Z320]

How does a Diesel engine stop dieseling?  Easy: stop the fuel (Diesel) suply.

That's what a lot of carb producers did with the petrol on carbs to avoid any discussion about "why".

On my mate Michael's TR6 the problem was only sometimes but has been grown more and more with the years.

No matter what he did against it, even driving with a mix with airplan fuel 160 ROZ.

[trchris]

Anti run on valves were standard on some Austin Rover models in the 80s as were anti knock sensors so there has always been a bit of a problem with running on and pinking 

Chris

[Andy Moltu]

I think they were fitted to Metros and possibly Maestro/Montego carbs

[Andy Moltu]

The spring loaded valve on the butterfly was more to do with emission reduction on overrun.

There is also a valve which opens and allows air to be drawn into the inlet manifolds to bi-pass the carbs so fuel isn’t drawn from the carbs when switched off

[Dic Doretti]

          I fitted an anti run on valve to an MGA which had a bad running on problem. It fitted into the inlet manifold and when the engine was turned off it let air in making the mixture too lean for the engine to run. The MGA had been used for racing and I think the valve came from a Fiesta.

          Cheers

          Richard

[Z320]

This way is the idea

[harlequin]

9 hours ago, Z320 said:

This way is the idea

That's a rather novel idea, I quite like it 

The anti run on system of my 73 TR6 has a valve that admits air into the system but it also closes the float chamber vent while putting a vacuum on the  float chamber which draws fuel away from the jet thereby starving the engine of fuel.

George

[Z320]

Idea is from Mercedes Benz from the 80-ies

[harlequin]

2 hours ago, Z320 said:

Idea is from Mercedes Benz from the 80-ies

So is the valve made for CD Strombergs Marco?

[keith1948]

On 6/17/2025 at 2:18 PM, Andy Moltu said:

I think they were fitted to Metros and possibly Maestro/Montego carbs

I had one on an Austin Metro Van Den Plas engine. Somewhere in the garage I got one to fit to the TR but never got around to it.

Keith

[Z320]

Yes but no.

The ones I use on my SU HS6 have been made for a Stromberg,

the ones I use now for Michael‘s Strombergs have been made for Solex carbs.

I know, sounds confusing….

[Charlie D]

Hello Marco,

I've got Stromberg CD175s from a TR4 fitted to my 3A, the sort where the mixture is adjusted by lowering the jet from underneath. (Similar to the SU).

 I guess that the solenoid you show in your pictures is for the later type, where an Allen key through the top is used to make the adjustment.

Charlie.

[Z320]

Hi Charlie, 

it will be for the model with the brass covered plastic cap, shown on the photo 

Edited June 20, 2025 by Z320

[Z320]

Currently out for the 50th annivercery of the TR IG Südwest

at the Thüringer Wald I unplugged my petrol off valves.

The weather is HOT, we drive the TRs HOT

and my TR4A‘s engine stopps without any dieseling,

with 98 ROZ Super Plus or 95 ROZ Super E10.

 

[Z320]

Hi,

with all my other hobbies I have only a slowly progress with the Stromberg petrol switch off valves.

They will be made in 2 pieces, the inside pieces guide the petrol down and out of the carbs and have been done already.

But I noticed I did not work accurate enough (scrap, right side) and have to make them new (left side), one is done.

Ciao, Marco

 

[Z320]

Hi, 

first valve is ready, apart from the collection of o-rings I had to order 2 more sizes.....

The arrows should explain how the petrol flows

On this photo it looks hudge, but is only 85 mm long from the ground of the float jamber lid.

On a LHD TR6 his should not be a problem, perhaps on a RHD with its steering column?

This way the construction is very similar /re-invented?) to the construction

Mercedes Benz used in the mid 80-ies with Strombergs 175 CD on 4 cylinder engines?

Now the second holder has to be made, easy now.

My mate Michael and me are very excited for the first test.

Ciao, Marco

Edited July 21, 2025 by Z320

[Andy Moltu]

It seems a lot of effort. 
Running on is rarely sustained and if it were you could simply stall the engine by gently lifting the clutch (in gear with the brake on).

[John Morrison]

I love Marco’s engineering abilities I really do, and wish I could do half the things he can, but in you car with this issue, why wouldn’t you just put a switch to earth the coil?

John

[RobH]

55 minutes ago, John Morrison said:

why wouldn’t you just put a switch to earth the coil?

As Peter points out above John, running on is not due to ignition from the coil - it is due to a hot-spot in the engine and doesn't need a spark.